A method of delivering common data such as content to respective communication apparatuses by performing transmission and reception of data between the communication apparatuses is known. In this method, the communication apparatus performs a data relay by transmitting received data to another communication apparatus. Information (receipt information) related to the reception of the data relay is used as a material for provision of a reward to the communication apparatus contributing to the data relay, or as a material for analysis of delivery efficiency, marketing, or the like.
However, there is a possibility of the receipt information being altered. Thus, it is desirable to collect the receipt information while preventing the receipt information from being altered.